1. Field of the Invention
The present invention relates to a magnetic assembly structure used for a compact electric apparatus, a method of fabricating the magnetic assembly structure, and a compact electric apparatus adopting the magnetic assembly structure, and more particularly, in improvements to apparatus such as electroacoustic transducers and DC motors.
2. Description of the Related Art
It is well known that an electroacoustic transducer or a vibration motor which is a silent calling means can be used as an alarming source in a mobile communications apparatus. Both of these apparatus use a magnetic assembly structure.
When the magnetic assembly structure is used for an electroacoustic transducer, a pole piece located at the center of a yoke of a magnetic material on which a low profile cylindrical magnet is placed. A resin base is formed integrally with a plurality of feeder terminals. A previously wound air-core coil is inserted in the pole piece and end portions thereof are connected to the terminals by soldering.
To configure an electroacoustic transducer by using the magnetic assembly structure, a boss is integrally erected from the base at the outside of the low profile cylindrical magnet, and a vibratory plate of thin stainless steel or Permalloy(trademark) including a magnetic material is placed on the boss portion. A case with a sound hole is covers the vibratory plate.
Also, as another example of the magnetic assembly structure used for a flat DC vibration motor, a shaft holder is installed at the center of a bracket of a magnetic material and also used as the yoke on which a low cylindrical magnet is placed, and a shaft is fixed to the shaft holder. Then, an eccentric rotor is rotatably installed on the shaft, and is covered by a low profile case.
However, according to recent trends in making a small and light mobile communications apparatus such as mobile phones and in the automation of assembly processes, magnetic assemblies are becoming more compact and an easy reflow soldering type is needed.
However, when the above magnetic assembly structure is used, the magnetic field may deteriorate due to high temperature during reflow soldering.
Also, according to recent trends in the automation of production processes and in low power consumption, the yoke and terminals are connected by a signal lead frame and integrally formed by using resin. Then, the connection portions therebetween are cut. Since the feeder terminal is formed of the same magnetic body (steel plate) as the yoke, the sectional surface of the feeder terminal may be corroded, making reflow soldering difficult. Also, since the feeder terminal is thick, solderability deteriorates. Accordingly, soldering for a longer time is needed so that the effect of thermal insulation is lowered.
Since the yoke serves as a magnetic path for the magnet, a yoke having a thickness at which the magnetic flux is not saturated is needed. Thus, it is not preferred to make the yoke by using a material having the same thickness as that of the feeder terminal.
To solve the above problems, it is an object of the present invention to provide a magnetic assembly structure having a superior reflow soldering feature considering thermal insulation of a magnet, in which the terminal is formed to be thin and easy to solder so that reflow soldering can be easily performed, and simultaneously, the yoke is formed to be appropriately thick to secure a magnetic path, a method of fabricating the magnetic assembly structure, and an electric apparatus using the magnetic assembly structure.
Accordingly, to achieve the above object, there is provided a magnetic assembly structure comprising a yoke formed of a magnetic material to be connected on a first lead frame and separated at a connection portion, at least one feeder terminal having an anticorrosion feature and exhibiting soderability, formed to be connected on a second lead frame thinner than the first lead frame and to be separated at a connection portion, at least one feeder terminal being arranged to be insulated from the yoke, a base formed of anti-solderability resin for insulating at least a part between the yoke and the terminal, in which the connection portion of the yoke to be separated is incorporated not to protrude outside, and a ring type magnet arranged above the yoke.
It is preferred in the present invention that the feeder terminal is formed of a thin German silver plate and the yoke is formed of a anti-corrosion processed steel plate.
Also, it is preferred in the present invention that the magnet is slightly separated from the yoke so that reflow soldering is possible.
Also, it is preferred in the present invention that the overall shape of the plan view is rectangular and a mounting portion including a feeder terminal is arranged at each corner of the rectangular shape.
Also, it is preferred in the present invention that the mounting portion including the feeder terminal does not protrude outside by the rectangular corners.
To achieve the above object, there is provided a method of fabricating a magnetic assembly structure which is achieved by forming a first lead frame by installing a plurality of yokes connected by connection portions at a predetermined pitch, forming a second lead frame by installing a plurality of yokes connected by connection portions at a predetermined pitch, insulating at least a part of the first and second lead frames and forming an integrated base out of anti-solderability resin by injection-molding, and separating each of installation portions to form the yoke and feeder terminal having a predetermined shape.
To achieve the above object, there is provided an electric apparatus including a magnetic assembly structure which comprises a yoke formed of a magnetic material to be connected to a first lead frame and separated at a connection portion, at least one feeder terminal having an anticorrosion feature and exhibiting solderability, formed to be connected on a second lead frame thinner than the first lead frame and to be separated at a connection portion, at least one feeder terminal being arranged to be insulated from the yoke, a base for insulating at least a part between the yoke and the terminal, formed of anti-solderability resin into which the connection portion of the yoke to be separated is incorporated not to protrude outside, and a ring type magnet arranged above the yoke, wherein the electric apparatus is an electroacoustic transducer.
To achieve the above object, there is provided an electric apparatus including a magnetic assembly structure which comprises a yoke formed of a magnetic material to be connected on a first lead frame and separated at a connection portion, at least one feeder terminal having an anticorrosion feature and exhibiting soderability, formed to be connected on a second lead frame thinner than the first lead frame and to be separated at a connection portion, at least one feeder terminal being arranged to be insulated from the yoke, a base for insulating at least a part between the yoke and the terminal, formed of anti-solderability resin into which the connection portion of the yoke to be separated is incorporated not to protrude outside, and a ring type magnet arranged above the yoke, wherein the electric apparatus is a DC motor.
It is preferred in the present invention that the DC motor is a flat vibratory motor, the outside of the DC motor is formed of resin to be non-circular, and in which the feeder terminal is arranged in the corner of the DC motor and the outside of the DC motor is exposed laterally.